In the planned research, two psychophysiological hypotheses are to be tested. The first hypothesis is that visual imaging is a psychological process with physiological underpinnings which lie not only in the central nervous system, but also in the centrifugally conducting fibers of the optic nerve and in the retina of the eye. Two studies are planned as tests of this first hypothesis: Both experiments follow up a recent electroretinographic study in which two subjects with dilated pupils were instructed to image a light flash as brighter or dimmer. For both subjects, imaging consistently altered the amplitude of the electroretinogram triggered by the flash. The aim of the first follow-up experiment is to characterize (a) visual images which increase the amplitude of the light-triggered electroretinogram and (b) visual images which decrease it. The aim of the second follow-up test of the first hypothesis is to determine whether better visual imagers, who subjectively report that they image more rapidly and more vividly, are subjects whose images produce larger changes in the light-triggered electroretinogram. The second hypothesis, a corollary of the first hypothesis that visual imaging induces retinal as well as central effects, represents an attempt to explain why better visual imagers have recently been identified as subjects who can better control their heart rates, skin temperatures, and other peripheral effects of the autonomic nervous system. This second hypothesis to be tested is that the better visual images of the second experiment, those imagers who have developed better control over the centrifugal fibers to the retina and who can induce larger electroretinographic effects through visual imaging, would be likely to be the same subjects who have developed better control over the centrifugal fibers in the autonomic nervous system and who can (in a third experiment) voluntarily induce larger autonomic effects.